U.S. patent number 3,995,086 [Application Number 05/591,095] was granted by the patent office on 1976-11-30 for shaped articles of hydraulic cement compositions and method of making same.
Invention is credited to Charles E. Cornwell, Mark Plunguian.
United States Patent |
3,995,086 |
Plunguian , et al. |
November 30, 1976 |
Shaped articles of hydraulic cement compositions and method of
making same
Abstract
Shaped articles such as tiles and panels are produced from
calcium aluminate cement motars by casting in a mold with a glossy
water-repellent synthetic polymer surface to yield castings with
highly reflective glassy surfaces. The calcium aluminate layer need
only be several mils thick with the rest of the mold volume being
filled with other cementitious compositions. Color pigments may be
added to the calcium aluminate slurry to yield castings with
brilliant glassy colored surfaces.
Inventors: |
Plunguian; Mark (Alexandria,
VA), Cornwell; Charles E. (Alexandria, VA) |
Family
ID: |
24365040 |
Appl.
No.: |
05/591,095 |
Filed: |
June 27, 1975 |
Current U.S.
Class: |
428/312.4;
156/247; 264/338; 428/697; 156/245; 249/134; 428/409; 428/701 |
Current CPC
Class: |
B28B
7/0067 (20130101); B28B 7/348 (20130101); B28B
7/364 (20130101); C04B 28/02 (20130101); C04B
28/06 (20130101); C04B 41/009 (20130101); C04B
41/508 (20130101); C04B 41/65 (20130101); C04B
28/06 (20130101); C04B 14/06 (20130101); C04B
14/30 (20130101); C04B 41/508 (20130101); C04B
41/4505 (20130101); C04B 28/02 (20130101); C04B
24/26 (20130101); C04B 38/10 (20130101); C04B
41/009 (20130101); C04B 28/04 (20130101); C04B
2111/00336 (20130101); Y10T 428/249968 (20150401); Y10T
428/31 (20150115) |
Current International
Class: |
C04B
28/00 (20060101); C04B 28/06 (20060101); B28B
7/34 (20060101); B28B 7/36 (20060101); B28B
7/00 (20060101); C04B 41/65 (20060101); C04B
41/50 (20060101); C04B 41/60 (20060101); C04B
41/45 (20060101); B32B 005/18 (); B29B 001/00 ();
B28B 007/36 (); B28B 007/34 () |
Field of
Search: |
;428/409,539,310,311,446,522,538 ;156/245-247,243
;264/220,228,226,227,213,74,DIG.148,DIG.57,338 ;259/107
;249/134 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Dier; Philip
Claims
We claim:
1. A shaped article of calcium aluminate cementitious composition
with a reflective glossy surface.
2. A shaped article according to claim 1 in which the reflective
calcium aluminate cementitious composition is backed with a
portland cement composition.
3. A shaped article according to claim 2 in which the portland
cement composition contains polyvinyl acetate.
4. A shaped article according to claim 3 in which the portland
cement composition is aerated.
5. A shaped article according to claim 1 in which the reflective
calcium aluminate cementitious composition is backed by a gypsum
cement composition.
6. A shaped article according to claim 1 in which the calcium
aluminate cementitious composition comprises the addition of
microcrystalline silica particles.
7. A shaped article according to claim 1 in which the calcium
aluminate cementitious composition comprises the addition of color
pigments.
8. A process for producing a shaped article of calcium aluminate
cementitious composition with a reflective surface comprising the
steps of forming an aqueous calcium aluminate cementitious slurry
composition, casting this aqueous slurry in a synthetic polymer
mold, or a steel mold lined with a synthetic polymer, said polymer
being selected from the group comprising polystyrene and
polypropylene, filling the mold with the aqueous cementitious
composition, curing the casting thus formed, and then removing the
cured casting from the mold.
9. A process for producing a shaped article with a reflective
surface according to claim 8 comprising the steps of casting a thin
coating of calcium aluminate aqueous composition in a synthetic
polymer mold and completing the filling of the mold by backing this
thin coating with a portland cement composition.
Description
BACKGROUND OF THE INVENTION
A primary object of the invention is to provide a shaped article of
cementitious material with a least one highly reflective glassy
surface, useful for decorative and protective purposes such as
indoor and outdoor wall panelling, roofing tiles on buildings, and
the like.
Another object of the present invention is to provide a novel
method for the production of shaped articles of cementitious
material having highly reflective, glassy surfaces,
SUMMARY OF THE INVENTION
When aqueous slurries of hydraulic cements, such as portland
cement, calcium aluminate cement, or gypsum cement, either neat or
as a mortar, are cast in a mold, the cured castings assume the
shape of the mold. If the surfaces of the mold are smooth, and
these surfaces are treated with release agents, the surfaces of the
castings are smooth, but are dull, nonreflective, non-glossy. We
have now found that if the surfaces of the mold consist of a glassy
synthetic polymer which is naturally repellent to aqueous
compositions, such as polypropylene or polystyrene, and the
cementitious material is calcium aluminate, then the casting, after
curing, assumes a highly reflective glassy appearance wherever the
aqueous slurry had been in contact with the reflective glossy
polymeric composition. The calcium aluminate cement slurry not in
contact with the glossy polymer surface, cures to a dull finish the
same as the other cements.
Of all the hydraulic cements investigated, only calcium aluminate
showed this property of assuming a highly reflective glassy surface
upon curing the casting in a mold with a reflective glossy
water-repellent polymeric surface. These are the so-called
high-alumina cements obtained by fusing a mixture of aluminous and
calcareous materials and grinding the resulting product to a fine
powder. Two general types of calcium aluminate cements are produced
commercially. One type is produced by fusing naturally occurring
bauxite with limestone in a 1:1 molar ratio of lime to alumina. A
typical analyses of such a cement by weight percent is 40% Al.sub.2
O.sub.3, 38% CaO, 11% Fe.sub.2 O.sub.3, 4% FeO, about 5% SiO.sub.2,
and about 2% TiO.sub.2. The other type is made by fusing together
pure alumina and lime to give a white hydraulic cement with a 1:2.5
molar ratio of lime to alumina. A typical analysis of such a cement
by weight percent is 72% Al.sub.2 O.sub.3 and 26% CaO. Either type
may be used for our purpose.
Commercial examples of the first type are:
Lumnite (Atlas Cement Company), and
Fondu cement (Lone Star Lafarge Co.).
Commercial examples of the second type are:
Alcoa cement CA-25 (Aluminum Corporation of America), and
Secar 250 (Lone Star Lafarge Co.).
The glassy surfaces may be produced in any color by the addition to
the calcium aluminate slurry color pigments which are insoluble in
water, chemically inactive, are light fast, and are of fine
particle size. These are generally the iron oxides for red, yellow,
buff, brown, gray, and black; manganese oxide for black and brown;
chromium oxide for green; and cobalt blue for blue. Titanium
dioxide may be added to lighten the color of ferric oxide occurring
in the bauxite, and to produce lighter pastel shades with the color
pigments. Marble effects may be produced by blending.
The calcium aluminate slurry may be used neat or as a mortar with
silica sand. Finely-divided silica particles give a harder, more
durable, scratch-resistant surface, with the same highly reflective
glassy surface properties. These fine particles may be produced by
grinding or by using the naturally occurring microcrystalline
silica, such as those located near Hot Springs, Arkansas (Novacite
silicas, Malvern Minerals Company).
Calcium aluminate cements are more expensive than portland cement,
or gypsum cement. It is therefore desirable to use calcium
aluminate only for the surface. A layer of about 3-6 mils thick is
sufficient to give the highly reflective glassy surface in any
desired color. After applying the base coat of calcium aluminate
slurry, either by slush coating, spraying or brushing, it is
allowed to set for about 15 to 30 minutes. It is important not to
allow this base coat to set completely and dry, since it then
begins to flake off and does not yield the glassy finish. Then,
while the prime coat is still moist, the mold is filled with the
bulk of the cement. A portland cement mortar or concrete gives an
overall strong, durable shaped article. For a lower density
composition one of the light weight aggregates may be used with the
portland cement, such as perlite or expanded shale. A preferred
composition is to use a portland cement mortar with the addition of
poly(vinyl acetate) emulsion. Without aeration, the poly(vinyl
acetate) aids in increasing the strength of the composition and
helps to bond the portland cement to the calcium aluminate layer.
When this slurry is foamed by aeration, for example by means of the
stirring and aerating device disclosed in our copending application
Ser. No. 509,940, filed Sept. 27, 1974, the volume may be about
doubled by the generation of stable air cells, thus greatly
reducing the density of the composition.
The presently preferred synthetic polymer for the glossy repellent
surface is polystyrene. Biaxially oriented sheeting may be
thermoformed to the shape of the mold. This may be used as an
insert to make repeated castings. After the surface loses its
luster, a new insert is used, while the old plastic is reground and
resheeted. Another approach is to spray a solution of polystyrene
in toluene or xylene on the mold and leave a repellent glossy
surface after evaporation of the solvent.
The invention will be further illustrated by the following
examples, in which all parts are by weight. Other synthetic
polymers with water repellent surfaces may be used, such as
polypropylene.
DETAILED DESCRIPTION OF THE INVENTION
Table I
__________________________________________________________________________
Examples of compositions of variously colored glassy coatings, in
parts by weight.
__________________________________________________________________________
Example No. 1 2 3 4 5 6 7 Alcoa cement CA-25 100 -- -- -- -- -- --
Lumnite cement -- 100 100 100 100 100 100 Novacite 200 silica 50 50
100 50 20 -- -- fine silica sand -- -- -- -- 100 100 100 chromic
oxide green 5 -- 5 -- -- -- -- cement black -- 5 -- -- -- -- --
ferric oxide red -- -- -- 5 2.5 -- -- titanium dioxide -- -- -- --
-- -- 5 water 50 50 80 80 45 45 50 anionic surfactant 0.04 0.04
0.04 0.04 0.04 0.04 0.04
__________________________________________________________________________
The slurry compositions shown in Table I were slush-coated in
polystyrene molds. The excess slurry was poured off and the thin
coatings were allowed to set for 20-30 minutes. A slurry was then
mixed of 100 parts portland cement, 100 parts coarse sand, 100
parts fine sand, 80 parts water and 10 parts poly(vinyl acetate)
emulsion. A thin coating of this mixture was applied over the
calcium aluminate layer in the mold. The rest of the portland
cement mixture was then aerated vigorously to foam and thus about
double the volume. This low density dispersion was then used to
fill the molds. After standing for 24 hours at room temperature,
the cured pieces were removed from the molds. They showed variously
colored highly reflective, glassy surfaces, corresponding to the
shape of the molds. Example 1 was a light green color. Example 3
was a darker green. Example 2 was jet black. Examples 4 and 5 were
different shades of red. Example 6 was brownish in color, while
Example 7 was a very light buff color.
EXAMPLE 8
A slurry composition corresponding to Example 6 was slush-coated in
a polystyrene mold. After a 30 minute set at room temperature, the
mold was filled with a slurry of 200 parts gypsum cement in 85
parts water. The composition was allowed to cure for 24 hours. It
was then removed to yield a casting with a brown, highly reflecting
glassy surface.
EXAMPLE 9
A slurry composition corresponding to Example 3 was sprayed on the
interior surfaces of a polystyrene mold to leave a thin uniform
film of the calcium aluminate slurry. After 15 minutes at room
temperature, the mold was filled with the portland cement
composition used for examples 1 to 7. It was allowed to cure for 24
hours and was then removed from the mold to yield a casting with a
highly reflective, glassy surface.
EXAMPLE 10
A 25% solution of polystyrene in toluene was sprayed into a steel
mold. It was left at room temperature until the solvent had
evaporated to leave a continuous glossy film of polystyrene. The
treated mold was then used in a manner similar to the description
in Example 9 and yielded after curing a casting with a highly
reflective, glassy finish.
It should be appreciated that those skilled in the art could
suggest various changes and modifications of the presently
preferred embodiments of the invention after being apprised of this
invention. It is intended to encompass all such changes and
modifications as fall within the scope and spirit of the appended
claims.
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